In recent years, various applications of near-infrared absorbing materials (heat ray-shielding materials) that absorb near-infrared radiation have been proposed; however, there is a strong demand for a near-infrared absorbing material that exhibits even superior performance.
For example, materials such as methacrylic resins and polycarbonate resins have been used in so-called glazing applications including windows of buildings and vehicles such as automobiles as well as roof windows, doors and roof domes, and there is a demand for a material that is capable of inhibiting an increase in the room temperature while allowing visible light to be sufficiently taken in.
Also, in plant cultivation, greenhouses and vinyl houses are actively used for the purposes of, for example, improving the yields of agricultural crops and shifting the harvest time, and there is a demand for a film that effectively shields heat rays without substantially hindering the transmission of visible light required for plant growth.
Further, near-infrared radiation is often used for driving and stopping electric appliances that perform recording and playing of an information recording medium such as magnetic tape and, in such electric appliances, near-infrared radiation coming from outside need to be blocked.
In addition, there is a problem that a near-infrared light emitted from a plasma display acts on its surrounding electric appliances that utilizes near-infrared remote control, such as a cordless phone and a video tape recorder, to cause malfunction. Therefore, there is a demand for a plasma display filter that exerts a near-infrared absorbing effect.
Furthermore, recently, reading of information signals such as bar codes is increasingly performed using a near-infrared light so as to prevent malfunction, ensure the security and make printed matters such as bar codes inconspicuous, and near-infrared absorbing inks and the like are used therein.
In the near-infrared absorbing materials used in these applications, conventionally, near-infrared absorbing pigments that absorb near-infrared radiation, such as cyanine-based pigments, phthalocyanine-based pigments, polymethine-based pigments, squarylium-based pigments, porphyrin-based pigments, metal dithiol complex-based pigments, diimonium-based pigments and inorganic oxide particles, have been employed (Patent Document 1).
However, when these near-infrared absorbing pigments are used as near-infrared absorbing materials, they are often used in combination with a synthetic resin such as a thermoplastic resin and, in such cases, there is a problem in the compatibility with the resin, and the pigments have an absorption wavelength in the visible light region and thus often impair the transparency and other physical properties of the resin. In addition, since these near-infrared absorbing pigments have a narrow absorption spectral width and do not show sufficient near-infrared light shielding effect, their near-infrared absorbing capacities are not satisfactory. Particularly, there is a demand for a material that shows efficient absorption in the near-infrared region.
Meanwhile, in the compound described in Patent Document 2, an alkoxy group is not essential in the phthalocyanine-constituting ring and an image-forming toner is the intended use of the compound; therefore, the findings of the present invention cannot be obtained.